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Galor A. My eyes feel dry. Is it all in my head? Indian J Ophthalmol 2024; 72:769-771. [PMID: 38804795 PMCID: PMC11232870 DOI: 10.4103/ijo.ijo_284_24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2024] Open
Affiliation(s)
- Anat Galor
- Surgical Services, Miami Veterans Affairs Hospital, Miami, FL, USA
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami, Miami, FL, USA
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2
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Hegarty DM, Carroll JR, Nguyen D, Halls VS, Robbins DI, Price TJ, Dussor G, Aicher SA. Resveratrol increases tear production and ocular pain after corneal abrasion in male, but not female, rats using a photorefractive keratectomy model. Exp Eye Res 2022; 225:109281. [PMID: 36265575 DOI: 10.1016/j.exer.2022.109281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 09/23/2022] [Accepted: 10/13/2022] [Indexed: 12/29/2022]
Abstract
Photorefractive keratectomy (PRK) is an alternative to LASIK and can cause intense acute pain that is often not relieved by standard treatments. To assess potential therapeutics for this type of acute pain, appropriate preclinical models are needed. We describe a preclinical corneal abrasion rat model that simulates the initial stages of PRK surgery and demonstrates similar pain and tear dysfunction as seen clinically. We used both behavioral and homeostatic assays to determine the therapeutic potential of resveratrol on pain and tear production. Studies were conducted in male and female Sprague-Dawley rats. Heptanol was applied to one eye and the superficial corneal epithelium was removed, mimicking the abrasion used in PRK. Spontaneous pain was assessed with orbital tightening (OT) scores for 7 days. Topical resveratrol increased OT scores sex-specifically in abraded males, but not females, at 72 h and 1 week after abrasion. Resveratrol increased tear production in abraded males, with no effect in abraded females. There was no correlation between OT score at 1 week and tear production measurements, demonstrating no relationship between spontaneous ocular pain and tear dysfunction in this model. These findings demonstrate the usefulness of our corneal abrasion preclinical PRK model for the assessment of ocular pain therapeutics and indicate that topical resveratrol may not be useful for managing PRK-induced pain.
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Affiliation(s)
- Deborah M Hegarty
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA
| | - James R Carroll
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Dennis Nguyen
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Victoria S Halls
- Medicinal Chemistry Core, Oregon Health & Science University, Portland, OR, 97239, USA
| | | | - Theodore J Price
- Ted's Brain Science, Inc., Dallas, TX, 75252, USA; School of Behavioral and Brain Sciences, Department of Neuroscience, Center for Advanced Pain Studies, University of Texas at Dallas, Richardson, TX, 75080, USA
| | - Gregory Dussor
- Ted's Brain Science, Inc., Dallas, TX, 75252, USA; School of Behavioral and Brain Sciences, Department of Neuroscience, Center for Advanced Pain Studies, University of Texas at Dallas, Richardson, TX, 75080, USA
| | - Sue A Aicher
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA.
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3
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Kurganov E, Okamoto K, Miyata S. Distribution of TRPM8-expressing trigeminal nerve fibers in the pons and medulla oblongata of the mouse brain. J Chem Neuroanat 2022; 122:102104. [PMID: 35561876 DOI: 10.1016/j.jchemneu.2022.102104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 05/05/2022] [Accepted: 05/06/2022] [Indexed: 11/16/2022]
Abstract
Transient receptor potential melastatin 8 (TRPM8), a cold-mediated ion channel, is well known to be expressed in primary sensory neurons; however, limited information is currently available on the distribution of TRPM8-expressing trigeminal nerve fibers in the brainstem. The present study showed the distribution of TRPM8-expressing fibers in the pons and medulla oblongata of the TRPM8 KO mice engineered by knocking in EGFP at the frame of the start codon of TRPM8. In addition, TRPM8-expressing fibers were also observed in the brachium pontis, middle cerebellar peduncle, the sensory root of the trigeminal nerve, and spinal trigeminal tract (sp5). Furthermore, TRPM8-expressing nerve fibers surrounded the somata of HuC/D-positive neurons in the sp5. Moreover, the distribution of TRPM8-expressing fibers from rostral to caudal was visualized in sagittal sections of the mouse brain. The present results also revealed that a high number of TRPM8-expressing fibers colocalized with CTB-labeled fibers in the sp5 following an injection of CTB into the whisker compared to mice's eye and ear. These results show the distribution pathway of TRPM8-expressing fibers in the pons and medulla oblongata and possible involvement in peripheral signaling from the trigeminal nerve.
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Affiliation(s)
- Erkin Kurganov
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan.
| | - Kaho Okamoto
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
| | - Seiji Miyata
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
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4
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Pondelis NJ, Moulton EA. Supraspinal Mechanisms Underlying Ocular Pain. Front Med (Lausanne) 2022; 8:768649. [PMID: 35211480 PMCID: PMC8862711 DOI: 10.3389/fmed.2021.768649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 12/27/2021] [Indexed: 12/04/2022] Open
Abstract
Supraspinal mechanisms of pain are increasingly understood to underlie neuropathic ocular conditions previously thought to be exclusively peripheral in nature. Isolating individual causes of centralized chronic conditions and differentiating them is critical to understanding the mechanisms underlying neuropathic eye pain and ultimately its treatment. Though few functional imaging studies have focused on the eye as an end-organ for the transduction of noxious stimuli, the brain networks related to pain processing have been extensively studied with functional neuroimaging over the past 20 years. This article will review the supraspinal mechanisms that underlie pain as they relate to the eye.
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Affiliation(s)
- Nicholas J Pondelis
- Brain and Eye Pain Imaging Lab, Pain and Affective Neuroscience Center, Department of Anesthesiology, Critical Care and Pain Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States
| | - Eric A Moulton
- Brain and Eye Pain Imaging Lab, Pain and Affective Neuroscience Center, Department of Anesthesiology, Critical Care and Pain Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States.,Department of Ophthalmology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States
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5
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Puja G, Sonkodi B, Bardoni R. Mechanisms of Peripheral and Central Pain Sensitization: Focus on Ocular Pain. Front Pharmacol 2021; 12:764396. [PMID: 34916942 PMCID: PMC8669969 DOI: 10.3389/fphar.2021.764396] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 11/09/2021] [Indexed: 12/14/2022] Open
Abstract
Persistent ocular pain caused by corneal inflammation and/or nerve injury is accompanied by significant alterations along the pain axis. Both primary sensory neurons in the trigeminal nerves and secondary neurons in the spinal trigeminal nucleus are subjected to profound morphological and functional changes, leading to peripheral and central pain sensitization. Several studies using animal models of inflammatory and neuropathic ocular pain have provided insight about the mechanisms involved in these maladaptive changes. Recently, the advent of new techniques such as optogenetics or genetic neuronal labelling has allowed the investigation of identified circuits involved in nociception, both at the spinal and trigeminal level. In this review, we will describe some of the mechanisms that contribute to the perception of ocular pain at the periphery and at the spinal trigeminal nucleus. Recent advances in the discovery of molecular and cellular mechanisms contributing to peripheral and central pain sensitization of the trigeminal pathways will be also presented.
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Affiliation(s)
- Giulia Puja
- Department of Life Sciences, University of Modena and Reggio Emilia, Emilia-Romagna, Italy
| | - Balazs Sonkodi
- Department of Health Sciences and Sport Medicine, University of Physical Education, Budapest, Hungary
| | - Rita Bardoni
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Emilia-Romagna, Italy
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6
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Sugimoto M, Takahashi Y, Sugimura YK, Tokunaga R, Yajima M, Kato F. Active role of the central amygdala in widespread mechanical sensitization in rats with facial inflammatory pain. Pain 2021; 162:2273-2286. [PMID: 33900711 PMCID: PMC8280967 DOI: 10.1097/j.pain.0000000000002224] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 01/01/2021] [Accepted: 01/26/2021] [Indexed: 01/19/2023]
Abstract
ABSTRACT Widespread or ectopic sensitization is a hallmark symptom of chronic pain, characterized by aberrantly enhanced pain sensitivity in multiple body regions remote from the site of original injury or inflammation. The central mechanism underlying widespread sensitization remains unidentified. The central nucleus of the amygdala (also called the central amygdala, CeA) is well situated for this role because it receives nociceptive information from diverse body sites and modulates pain sensitivity in various body regions. In this study, we examined the role of the CeA in a novel model of ectopic sensitization of rats. Injection of formalin into the left upper lip resulted in latent bilateral sensitization in the hind paw lasting >13 days in male Wistar rats. Chemogenetic inhibition of gamma-aminobutyric acid-ergic neurons or blockade of calcitonin gene-related peptide receptors in the right CeA, but not in the left, significantly attenuated this sensitization. Furthermore, chemogenetic excitation of gamma-aminobutyric acid-ergic neurons in the right CeA induced de novo bilateral hind paw sensitization in the rats without inflammation. These results indicate that the CeA neuronal activity determines hind paw tactile sensitivity in rats with remote inflammatory pain. They also suggest that the hind paw sensitization used in a large number of preclinical studies might not be simply a sign of the pain at the site of injury but rather a representation of the augmented CeA activity resulting from inflammation/pain in any part of the body or from activities of other brain regions, which has an active role of promoting defensive/protective behaviors to avoid further bodily damage.
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Affiliation(s)
- Mariko Sugimoto
- Center for Neuroscience of Pain and Department of Neuroscience, The Jikei University School of Medicine, Tokyo, Japan
- Department of Anesthesiology, Teikyo University School of Medicine, Tokyo, Japan
| | - Yukari Takahashi
- Center for Neuroscience of Pain and Department of Neuroscience, The Jikei University School of Medicine, Tokyo, Japan
| | - Yae K. Sugimura
- Center for Neuroscience of Pain and Department of Neuroscience, The Jikei University School of Medicine, Tokyo, Japan
| | - Ryota Tokunaga
- Center for Neuroscience of Pain and Department of Neuroscience, The Jikei University School of Medicine, Tokyo, Japan
| | - Manami Yajima
- Center for Neuroscience of Pain and Department of Neuroscience, The Jikei University School of Medicine, Tokyo, Japan
- Department of Dental Anesthesiology, School of Dental Medicine, Tsurumi University, Yokohama, Japan
| | - Fusao Kato
- Center for Neuroscience of Pain and Department of Neuroscience, The Jikei University School of Medicine, Tokyo, Japan
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Clinical Manifestation and Risk Factors Associated With Remission in Patients With Filamentary Keratitis. Am J Ophthalmol 2020; 218:78-83. [PMID: 32574776 DOI: 10.1016/j.ajo.2020.05.037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 05/25/2020] [Accepted: 05/25/2020] [Indexed: 11/23/2022]
Abstract
PURPOSE This study investigated the clinical manifestation and risk factors associated with remission in filamentary keratitis. DESIGN Retrospective, interventional, comparative case series. METHODS We retrospectively reviewed the medical records of 116 patients with filamentary keratitis diagnosed and treated between January 2012 and December 2018. We investigated the 5 causative factors including brain lesion, dry eye syndrome, autoimmune disease, ocular surgery or injury, and other conditions; treatment methods and duration; and remission status, and analyzed the risk factors associated with remission. RESULTS The mean age of the patients was 56.9 ± 19.1 years and the mean follow-up duration was 14.9 ± 22.8 months. The most common underlying condition associated with filamentary keratitis was identified as a brain lesion (36.2%), followed by dry eye syndrome (30.2%) and autoimmune disease (24.1%). A comparison of remission rates among the causative factors revealed that cases associated with brain lesions had significantly lower remission rates (33.3%) than those associated with other causative factors (>60%) (P = .001). After adjustment for sex, age, diabetes mellitus, and hypertension, the treatment failure rate in patients affected by brain lesions was 6.602-fold higher than that associated without brain lesion (P = .001). The treatment method-dependent differences in the remission rate were observed in brain lesion and dry eye syndrome (P = .041 and P = .005, respectively). CONCLUSIONS The most common condition leading to filamentary keratitis was a brain lesion, followed by dry eye syndrome and autoimmune disease. The treatment failure rate was statistically significantly low only in patients with filamentary keratitis associated with brain lesions.
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8
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Lan DY, Zhu PW, He Y, Xu QH, Su T, Li B, Shi WQ, Lin Q, Yang YC, Yuan Q, Fang JW, Li QH, Shao Y. Gray Matter Volume Changes in Patients With Acute Eye Pain: A Voxel-Based Morphometry Study. Transl Vis Sci Technol 2019; 8:1. [PMID: 30627476 PMCID: PMC6322711 DOI: 10.1167/tvst.8.1.1] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 10/21/2018] [Indexed: 02/06/2023] Open
Abstract
PURPOSE The present study was attempted to compare the differences in gray matter volume (GMV) between the acute eye pain (EP) patients and the healthy controls (HCs) using voxel-based morphometry (VBM), and to explore the relationship with clinical features and behavioral performance. METHODS A total of 24 patients (17 males, 7 females) with acute EP and 24 (17 males, 7 females) age-, sex-, and education-matched HCs were recruited from the Ophthalmology Department of the First Affiliated Hospital of Nanchang University. Functional magnetic resonance imaging (fMRI) scans were conducted in all subjects. We analyzed the original three-dimensional (3D) T1 brain images by VBM and compared the GMV values with the HCs. The acute EP patients can be distinguished from the HCs by receiver operating characteristic (ROC) curve. RESULTS Compared with HCs, the acute EP patients had significantly lower GMV values in the brain regions of the left cerebellum posterior lobe, the left limbic lobe, the right insula, the left insula, the left thalamus, the left caudate, and the right cuneus. In addition, the WMV values of the whole brain in acute EP patients decreased slightly. CONCLUSIONS These results demonstrated that the acute EP patients showed an abnormal reduction in GMV in some brain regions, which might provide valuable information for further exploration of underlying neural mechanisms. These abnormal brain regions may reflect the functional disorders of acute EP patients in somatosensory, motor, cognitive functions, and so on. TRANSLATIONAL RELEVANCE The VBM study provides a diagnostic method for identifying the cause of acute EP, additionally, a novel direction was presented for further exploration of underlying neural mechanisms of acute EP.
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Affiliation(s)
- Dong-Yi Lan
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang, Jiangxi, China
| | - Pei-Wen Zhu
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang, Jiangxi, China
| | - Ying He
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang, Jiangxi, China
| | - Qian-Hui Xu
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang, Jiangxi, China
| | - Ting Su
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang, Jiangxi, China
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Xiamen, Fujian Province, China
| | - Biao Li
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang, Jiangxi, China
| | - Wen-Qing Shi
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang, Jiangxi, China
| | - Qi Lin
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang, Jiangxi, China
| | - Yan-Chang Yang
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang, Jiangxi, China
| | - Qing Yuan
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang, Jiangxi, China
| | - Jian-Wen Fang
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang, Jiangxi, China
| | - Qing-Hai Li
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang, Jiangxi, China
| | - Yi Shao
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute, Nanchang, Jiangxi, China
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9
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Miyazawa Y, Takahashi Y, Watabe AM, Kato F. Predominant synaptic potentiation and activation in the right central amygdala are independent of bilateral parabrachial activation in the hemilateral trigeminal inflammatory pain model of rats. Mol Pain 2018; 14:1744806918807102. [PMID: 30270724 PMCID: PMC6243415 DOI: 10.1177/1744806918807102] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Nociceptive signals originating in the periphery are conveyed to the brain through specific afferent and ascending pathways. The spino-(trigemino-)parabrachio-amygdaloid pathway is one of the principal pathways mediating signals from nociception-specific ascending neurons to the central amygdala, a limbic structure involved in aversive signal-associated emotional responses, including the emotional aspects of pain. Recent studies suggest that the right and left central amygdala play distinct roles in the regulation of nociceptive responses. Using a latent formalin inflammatory pain model of the rat, we analyzed the right-left differences in synaptic potentiation at the synapses formed between the fibers from the lateral parabrachial nucleus and central amygdala neurons as well as those in the c-Fos expression in the lateral parabrachial nucleus, central amygdala, and the basolateral/lateral amygdala after formalin injection to either the right or left side of the rat upper lip. Although the single-sided formalin injection caused a significant bilateral increase in c-Fos-expressing neurons in the lateral parabrachial nucleus with slight projection-side dependence, the increase in the amplitude of postsynaptic excitatory currents and the number of c-Fos-expressing neurons in the central amygdala occurred predominantly on the right side regardless of the side of the inflammation. Although there was no significant correlation in the number of c-Fos-expressing neurons between the lateral parabrachial nucleus and central amygdala in the formalin-injected animals, these numbers were significantly correlated between the basolateral amygdala and central amygdala. It is thus concluded that the lateral parabrachial nucleus-central amygdala synaptic potentiation reported in various pain models is not a simple Hebbian plasticity in which raised inputs from the lateral parabrachial nucleus cause lateral parabrachial nucleus-central amygdala potentiation but rather an integrative and adaptive response involving specific mechanisms in the right central amygdala.
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Affiliation(s)
- Yuta Miyazawa
- 1 Department of Neuroscience, Jikei University School of Medicine, Tokyo, Japan.,2 Center for Neuroscience of Pain, Jikei University School of Medicine, Tokyo, Japan
| | - Yukari Takahashi
- 1 Department of Neuroscience, Jikei University School of Medicine, Tokyo, Japan.,2 Center for Neuroscience of Pain, Jikei University School of Medicine, Tokyo, Japan
| | - Ayako M Watabe
- 2 Center for Neuroscience of Pain, Jikei University School of Medicine, Tokyo, Japan.,3 Institute of Clinical Medicine and Research, Jikei University School of Medicine, Tokyo, Japan
| | - Fusao Kato
- 1 Department of Neuroscience, Jikei University School of Medicine, Tokyo, Japan.,2 Center for Neuroscience of Pain, Jikei University School of Medicine, Tokyo, Japan
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10
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Reiner A, Fitzgerald MEC, Del Mar N, Li C. Neural control of choroidal blood flow. Prog Retin Eye Res 2018; 64:96-130. [PMID: 29229444 PMCID: PMC5971129 DOI: 10.1016/j.preteyeres.2017.12.001] [Citation(s) in RCA: 121] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 11/28/2017] [Accepted: 12/01/2017] [Indexed: 02/07/2023]
Abstract
The choroid is richly innervated by parasympathetic, sympathetic and trigeminal sensory nerve fibers that regulate choroidal blood flow in birds and mammals, and presumably other vertebrate classes as well. The parasympathetic innervation has been shown to vasodilate and increase choroidal blood flow, the sympathetic input has been shown to vasoconstrict and decrease choroidal blood flow, and the sensory input has been shown to both convey pain and thermal information centrally and act locally to vasodilate and increase choroidal blood flow. As the choroid lies behind the retina and cannot respond readily to retinal metabolic signals, its innervation is important for adjustments in flow required by either retinal activity, by fluctuations in the systemic blood pressure driving choroidal perfusion, and possibly by retinal temperature. The former two appear to be mediated by the sympathetic and parasympathetic nervous systems, via central circuits responsive to retinal activity and systemic blood pressure, but adjustments for ocular perfusion pressure also appear to be influenced by local autoregulatory myogenic mechanisms. Adaptive choroidal responses to temperature may be mediated by trigeminal sensory fibers. Impairments in the neural control of choroidal blood flow occur with aging, and various ocular or systemic diseases such as glaucoma, age-related macular degeneration (AMD), hypertension, and diabetes, and may contribute to retinal pathology and dysfunction in these conditions, or in the case of AMD be a precondition. The present manuscript reviews findings in birds and mammals that contribute to the above-summarized understanding of the roles of the autonomic and sensory innervation of the choroid in controlling choroidal blood flow, and in the importance of such regulation for maintaining retinal health.
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Affiliation(s)
- Anton Reiner
- Department of Anatomy & Neurobiology, University of Tennessee, 855 Monroe Ave. Memphis, TN 38163, United States; Department of Ophthalmology, University of Tennessee, 855 Monroe Ave. Memphis, TN 38163, United States.
| | - Malinda E C Fitzgerald
- Department of Anatomy & Neurobiology, University of Tennessee, 855 Monroe Ave. Memphis, TN 38163, United States; Department of Ophthalmology, University of Tennessee, 855 Monroe Ave. Memphis, TN 38163, United States; Department of Biology, Christian Brothers University, Memphis, TN, United States
| | - Nobel Del Mar
- Department of Anatomy & Neurobiology, University of Tennessee, 855 Monroe Ave. Memphis, TN 38163, United States
| | - Chunyan Li
- Department of Anatomy & Neurobiology, University of Tennessee, 855 Monroe Ave. Memphis, TN 38163, United States
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11
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Tang LY, Li HJ, Huang X, Bao J, Sethi Z, Ye L, Yuan Q, Zhu PW, Jiang N, Gao GP, Shao Y. Assessment of synchronous neural activities revealed by regional homogeneity in individuals with acute eye pain: a resting-state functional magnetic resonance imaging study. J Pain Res 2018; 11:843-850. [PMID: 29719418 PMCID: PMC5916265 DOI: 10.2147/jpr.s156634] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Objective Previous neuroimaging studies have demonstrated that pain-related diseases are associated with brain function and anatomical abnormalities, whereas altered synchronous neural activity in acute eye pain (EP) patients has not been investigated. The purpose of this study was to explore whether or not synchronous neural activity changes were measured with the regional homogeneity (ReHo) method in acute EP patients. Methods A total of 20 patients (15 males and 5 females) with EP and 20 healthy controls (HCs) consisting of 15 and 5 age-, sex-, and education-matched males and females, respectively, underwent resting-state functional magnetic resonance imaging. The ReHo method was applied to assess synchronous neural activity changes. Results Compared with HCs, acute EP patients had significantly lower ReHo values in the left precentral/postcentral gyrus (Brodmann area [BA]3/4), right precentral/postcentral gyrus (BA3/4), and left middle frontal gyrus (BA6). In contrast, higher ReHo values in acute EP patients were observed in the left superior frontal gyrus (BA11), right inferior parietal lobule (BA39/40), and left precuneus (BA7). However, no relationship was found between the mean ReHo signal values of the different areas and clinical manifestations, which included both the duration and degree of pain in EP patients. Conclusion Our study highlighted that acute EP patients showed altered synchronous neural activities in many brain regions, including somatosensory regions. These findings might provide useful information for exploration of the neural mechanisms underlying acute EP.
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Affiliation(s)
- Li-Yuan Tang
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
| | - Hai-Jun Li
- Department of Radiology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
| | - Xin Huang
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
| | - Jing Bao
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
| | - Zubin Sethi
- The Department of Medicine, University of Miami, Coral Gables, FL, USA
| | - Lei Ye
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
| | - Qing Yuan
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
| | - Pei-Wen Zhu
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
| | - Nan Jiang
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
| | - Gui-Ping Gao
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
| | - Yi Shao
- Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
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12
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Réaux-Le Goazigo A, Labbé A, Baudouin C, Melik Parsadaniantz S. La douleur oculaire chronique : mieux la comprendre pour mieux la traiter. Med Sci (Paris) 2017; 33:749-757. [DOI: 10.1051/medsci/20173308020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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13
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Tamaddonfard E, Erfanparast A. Role of μ-opioid receptor in parafascicular nucleus of thalamus on morphine-induced antinociception in a rat model of acute trigeminal pain. VETERINARY RESEARCH FORUM : AN INTERNATIONAL QUARTERLY JOURNAL 2017; 8:29-34. [PMID: 28473894 PMCID: PMC5413308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2016] [Accepted: 10/10/2016] [Indexed: 10/25/2022]
Abstract
The parafascicular nucleus (PFN) of thalamus, as a supraspinal structure, has an important role in processing of nociceptive information. In addition, μ-opioid receptor contributes to supraspinal modulation of nociception. In the present study, the effects of microinjection of naloxone (a non-specific opioid-receptor antagonist) and naloxonazine (a specific μ-opioid receptor antagonist) were investigated on morphine-induced antinociception in a rat model of acute trigeminal pain. Right and left sides of PFN of thalamus were implanted with two guide cannulas. Acute trigeminal pain was induced by local corneal surface application of hypertonic saline and the number of eye wipes as a pain index was recorded for 30 sec. Microinjection of morphine at doses of 1, 2 and 4 μg per site significantly (p < 0.05) decreased the number of eye wipes. Alone microinjection of naloxone (4 μg per site) and naloxonazine (1 and 2 μg per site) significantly (p < 0.05) increased corneal pain severity. Prior microinjection of naloxone (2 and 4 μg per site) and naloxonazine (1 and 2 μg per site) significantly (p < 0.05) prevented the antinociceptive effect induced by morphine (4 μg per site). All the above-mentioned chemicals did not alter locomotor behavior in an open-field test. The results of the present study showed an antinociceptive effect of morphine at the PFN level of thalamus. Mu-opioid receptor of the PFN of thalamus may be involved in morphine-induced antinociception.
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Affiliation(s)
- Esmaeal Tamaddonfard
- Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran.
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Hegarty DM, Hermes SM, Yang K, Aicher SA. Select noxious stimuli induce changes on corneal nerve morphology. J Comp Neurol 2017; 525:2019-2031. [PMID: 28213947 DOI: 10.1002/cne.24191] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 02/09/2017] [Accepted: 02/10/2017] [Indexed: 11/10/2022]
Abstract
The surface of the cornea contains the highest density of nociceptive nerves of any tissue in the body. These nerves are responsive to a variety of modalities of noxious stimuli and can signal pain even when activated by low threshold stimulation. Injury of corneal nerves can lead to altered nerve morphology, including neuropathic changes which can be associated with chronic pain. Emerging technologies that allow imaging of corneal nerves in vivo are spawning questions regarding the relationship between corneal nerve density, morphology, and function. We tested whether noxious stimulation of the corneal surface can alter nerve morphology and neurochemistry. We used concentrations of menthol, capsaicin, and hypertonic saline that evoked comparable levels of nocifensive eye wipe behaviors when applied to the ocular surface of an awake rat. Animals were sacrificed and corneal nerves were examined using immunocytochemistry and three-dimensional volumetric analyses. We found that menthol and capsaicin both caused a significant reduction in corneal nerve density as detected with β-tubulin immunoreactivity 2 hr after stimulation. Hypertonic saline did not reduce nerve density, but did cause qualitative changes in nerves including enlarged varicosities that were also seen following capsaicin and menthol stimulation. All three types of noxious stimuli caused a depletion of CGRP from corneal nerves, indicating that all modalities of noxious stimuli evoked peptide release. Our findings suggest that studies aimed at understanding the relationship between corneal nerve morphology and chronic disease may also need to consider the effects of acute stimulation on corneal nerve morphology.
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Affiliation(s)
- Deborah M Hegarty
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, Oregon
| | - Sam M Hermes
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, Oregon
| | - Katherine Yang
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, Oregon
| | - Sue A Aicher
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, Oregon
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Galor A, Levitt RC, Felix ER, Sarantopoulos CD. What can photophobia tell us about dry eye? EXPERT REVIEW OF OPHTHALMOLOGY 2016; 11:321-324. [PMID: 28845186 DOI: 10.1080/17469899.2016.1222905] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Anat Galor
- Miami Veterans Administration Medical Center, 1201 NW 16th St, Miami, FL 33125.,Bascom Palmer Eye Institute, University of Miami, 900 NW 17 Street, Miami, FL, 33136
| | - Roy C Levitt
- Miami Veterans Administration Medical Center, 1201 NW 16th St, Miami, FL 33125.,Department of Anesthesiology, Perioperative Medicine and Pain Management, University of Miami Miller School of Medicine, Miami, FL.,John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL.,John T Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL
| | - Elizabeth R Felix
- Miami Veterans Administration Medical Center, 1201 NW 16th St, Miami, FL 33125.,Department of Physical Medicine and Rehabilitation, University of Miami Miller School of Medicine, Miami, FL
| | - Constantine D Sarantopoulos
- Miami Veterans Administration Medical Center, 1201 NW 16th St, Miami, FL 33125.,Department of Anesthesiology, Perioperative Medicine and Pain Management, University of Miami Miller School of Medicine, Miami, FL
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Aicher SA, Hermes SM, Hegarty DM. Denervation of the Lacrimal Gland Leads to Corneal Hypoalgesia in a Novel Rat Model of Aqueous Dry Eye Disease. Invest Ophthalmol Vis Sci 2016; 56:6981-9. [PMID: 26513503 DOI: 10.1167/iovs.15-17497] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
PURPOSE Some dry eye disease (DED) patients have sensitized responses to corneal stimulation, while others experience hypoalgesia. Many patients have normal tear production, suggesting that reduced tears are not always the cause of DED sensory dysfunction. In this study, we show that disruption of lacrimal innervation can produce hypoalgesia without changing basal tear production. METHODS Injection of a saporin toxin conjugate into the extraorbital lacrimal gland of male Sprague-Dawley rats was used to disrupt cholinergic innervation to the gland. Tear production was assessed by phenol thread test. Corneal sensory responses to noxious stimuli were assessed using eye wipe behavior. Saporin DED animals were compared to animals treated with atropine to produce aqueous DED. RESULTS Cholinergic innervation and acetylcholine content of the lacrimal gland were significantly reduced in saporin DED animals, yet basal tear production was normal. Saporin DED animals demonstrated normal eye wipe responses to corneal application of capsaicin, but showed hypoalgesia to corneal menthol. Corneal nerve fiber density was normal in saporin DED animals. Atropine-treated animals had reduced tear production but normal responses to ocular stimuli. CONCLUSIONS Because only menthol responses were impaired, cold-sensitive corneal afferents appear to be selectively altered in our saporin DED model. Hypoalgesia is not due to reduced tear production, since we did not observe hypoalgesia in an atropine DED model. Corneal fiber density is unaltered in saporin DED animals, suggesting that molecular mechanisms of nociceptive signaling may be impaired. The saporin DED model will be useful for exploring the mechanism underlying corneal hypoalgesia.
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Li C, Fitzgerald MEC, Del Mar N, Cuthbertson-Coates S, LeDoux MS, Gong S, Ryan JP, Reiner A. The identification and neurochemical characterization of central neurons that target parasympathetic preganglionic neurons involved in the regulation of choroidal blood flow in the rat eye using pseudorabies virus, immunolabeling and conventional pathway tracing methods. Front Neuroanat 2015; 9:65. [PMID: 26082687 PMCID: PMC4451581 DOI: 10.3389/fnana.2015.00065] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 05/08/2015] [Indexed: 11/13/2022] Open
Abstract
The choroidal blood vessels of the eye provide the main vascular support to the outer retina. These blood vessels are under parasympathetic vasodilatory control via input from the pterygopalatine ganglion (PPG), which in turn receives its preganglionic input from the superior salivatory nucleus (SSN) of the hindbrain. The present study characterized the central neurons projecting to the SSN neurons innervating choroidal PPG neurons, using pathway tracing and immunolabeling. In the initial set of studies, minute injections of the Bartha strain of the retrograde transneuronal tracer pseudorabies virus (PRV) were made into choroid in rats in which the superior cervical ganglia had been excised (to prevent labeling of sympathetic circuitry). Diverse neuronal populations beyond the choroidal part of ipsilateral SSN showed transneuronal labeling, which notably included the parvocellular part of the paraventricular nucleus of the hypothalamus (PVN), the periaqueductal gray, the raphe magnus (RaM), the B3 region of the pons, A5, the nucleus of the solitary tract (NTS), the rostral ventrolateral medulla (RVLM), and the intermediate reticular nucleus of the medulla. The PRV+ neurons were located in the parts of these cell groups that are responsive to systemic blood pressure signals and involved in systemic blood pressure regulation by the sympathetic nervous system. In a second set of studies using PRV labeling, conventional pathway tracing, and immunolabeling, we found that PVN neurons projecting to SSN tended to be oxytocinergic and glutamatergic, RaM neurons projecting to SSN were serotonergic, and NTS neurons projecting to SSN were glutamatergic. Our results suggest that blood pressure and volume signals that drive sympathetic constriction of the systemic vasculature may also drive parasympathetic vasodilation of the choroidal vasculature, and may thereby contribute to choroidal baroregulation during low blood pressure.
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Affiliation(s)
- Chunyan Li
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center Memphis, TN, USA
| | - Malinda E C Fitzgerald
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center Memphis, TN, USA ; Department of Biology, Christian Brothers University Memphis, TN, USA ; Department of Ophthalmology, University of Tennessee Health Science Center Memphis, TN, USA
| | - Nobel Del Mar
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center Memphis, TN, USA
| | - Sherry Cuthbertson-Coates
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center Memphis, TN, USA
| | - Mark S LeDoux
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center Memphis, TN, USA ; Department of Neurology, University of Tennessee Health Science Center Memphis, TN, USA
| | - Suzhen Gong
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center Memphis, TN, USA
| | - James P Ryan
- Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center Memphis, TN, USA
| | - Anton Reiner
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center Memphis, TN, USA ; Department of Ophthalmology, University of Tennessee Health Science Center Memphis, TN, USA
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Abstract
As the biological alarm of impending or actual tissue damage, pain is essential for our survival. However, when it is initiated and/or sustained by dysfunctional elements in the nociceptive system, it is itself a disease known as neuropathic pain. While the critical nociceptive system provides a number of protective functions, it is unique in its central role of monitoring, preserving and restoring the optical tear film in the face of evaporative attrition without which our vision would be non-functional. Meeting this existential need resulted in the evolution of the highly complex, powerful and sensitive dry eye alarm system integrated in the peripheral and central trigeminal sensory network. The clinical consequences of corneal damage to these nociceptive pathways are determined by the type and location of its pathological elements and can range from the spectrum known as dry eye disease to the centalised oculofacial neuropathic pain syndrome characterised by a striking disparity between the high intensity of symptoms and paucity of external signs. These changes parallel those observed in somatic neuropathic pain. When seen through the neuroscience lens, diseases responsible for inadequately explained chronic eye pain (including those described as dry eye) can take on new meanings that may clarify long-standing enigmas and point to new approaches for developing preventive, symptomatic and disease-modifying interventions for these currently refractory disorders.
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Affiliation(s)
- Perry Rosenthal
- Boston EyePain Foundation, Chestnut Hill, Massachusetts, USA
| | - David Borsook
- Center for Pain and the Brain, Boston Children's, MGH and McLean Hospitals, Harvard Medical School, Children's Medical Center, Boston, Massachusetts, USA
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Hegarty DM, Hermes SM, Largent-Milnes TM, Aicher SA. Capsaicin-responsive corneal afferents do not contain TRPV1 at their central terminals in trigeminal nucleus caudalis in rats. J Chem Neuroanat 2014; 61-62:1-12. [PMID: 24996127 DOI: 10.1016/j.jchemneu.2014.06.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Revised: 06/23/2014] [Accepted: 06/23/2014] [Indexed: 10/25/2022]
Abstract
We examined the substrates for ocular nociception in adult male Sprague-Dawley rats. Capsaicin application to the ocular surface in awake rats evoked nocifensive responses and suppressed spontaneous grooming responses. Thus, peripheral capsaicin was able to activate the central pathways encoding ocular nociception. Our capsaicin stimulus evoked c-Fos expression in a select population of neurons within rostral trigeminal nucleus caudalis in anesthetized rats. These activated neurons also received direct contacts from corneal afferent fibers traced with cholera toxin B from the corneal surface. However, the central terminals of the corneal afferents that contacted capsaicin-activated trigeminal neurons did not contain TRPV1. To determine if TRPV1 expression had been altered by capsaicin stimulation, we examined TRPV1 content of corneal afferents in animals that did not receive capsaicin stimulation. These studies confirmed that while TRPV1 was present in 30% of CTb-labeled corneal afferent neurons within the trigeminal ganglion, TRPV1 was only detected in 2% of the central terminals of these corneal afferents within the trigeminal nucleus caudalis. Other TRP channels were also present in low proportions of central corneal afferent terminals in unstimulated animals (TRPM8, 2%; TRPA1, 10%). These findings indicate that a pathway from the cornea to rostral trigeminal nucleus caudalis is involved in corneal nociceptive transmission, but that central TRP channel expression is unrelated to the type of stimulus transduced by the peripheral nociceptive endings.
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Affiliation(s)
- Deborah M Hegarty
- Department of Physiology and Pharmacology, Oregon Health & Science University, Mail code: L334, 3181 Sam Jackson Park Road, Portland, OR 97239-3098, United States.
| | - Sam M Hermes
- Department of Physiology and Pharmacology, Oregon Health & Science University, Mail code: L334, 3181 Sam Jackson Park Road, Portland, OR 97239-3098, United States.
| | - Tally M Largent-Milnes
- Department of Physiology and Pharmacology, Oregon Health & Science University, Mail code: L334, 3181 Sam Jackson Park Road, Portland, OR 97239-3098, United States.
| | - Sue A Aicher
- Department of Physiology and Pharmacology, Oregon Health & Science University, Mail code: L334, 3181 Sam Jackson Park Road, Portland, OR 97239-3098, United States.
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